Single Step Workflow

How to create the first workflow with a single node

Create the Workflow

A workflow is usually implemented as a class that inherits from Workflow. The class can define an arbitrary number of nodes, each of which is a class that extens NeuronAI\Workflow\Node.

First, let's create the MyWorkflow class:

Unix

php vendor/bin/neuron make:workflow App\\Neuron\\MyWorkflow

Windows

php .\vendor\bin\neuron make:workflow App\\Neuron\\MyWorkflow

Here is the simplest possible workflow:

namespace App\Neuron;

use NeuronAI\Workflow\Workflow;

class MyWorkflow extends Workflow
{
    protected function nodes(): array
    {
        return [
            new InitialNode(),
        ];
    }
}

Now let's create the node:

Unix

php vendor/bin/neuron make:node App\\Neuron\\InitialNode

Windows

php .\vendor\bin\neuron make:node App\\Neuron\\InitialNode

A Node is an invokable class to handle an incoming event, and return another event:

namespace App\Neuron;

use NeuronAI\Workflow\Node;
use NeuronAI\Workflow\StartEvent;
use NeuronAI\Workflow\StopEvent;
use NeuronAI\Workflow\WorkflowState;

class InitialNode extends Node
{
    public function __invoke(StartEvent $event, WorkflowState $state): StopEvent
    {
        $state->set('answer', 'Hello World!');
        
        return new StopEvent();
    }
}

This will print "Hello World!" to the console:

$finalState = MyWorkflow::make()->start()->getResult();

echo $finalState->get('answer'); // Print Hello World!

In this code we:

• Define a class MyWorkflow that inherits from Workflow

• Define a Node implementing the __invoke method

• The step takes an event as input, $event, which is an instance of StartEvent

• The Node adds a value to the state and returns a StopEvent

• We create an instance of MyWorkflow

• We start the workflow and get the result

• Print the result in the console

Type hint for events

The $event type (e.g. StartEvent) and -> StopEvent are essential to the way Workflows work. The expected types determine what event types will trigger a Node.

Event types are validated at compile time, so you will get an error message if for instance you return an event that is never consumed by another Node.

Start and Stop events

StartEvent and StopEvent are special events that are used to start and stop a workflow. The node that accepts a StartEvent will be triggered first by when you start the workflow. Returning a StopEvent will end the execution of the workflow and return the final state, even if other nodes remain un-executed.

Monitoring & Debugging

Before moving into the Workflow creation process, we recommend having the monitoring system in place. It could make the learning curve of how Workflow works much more easier. The best way to monitoring Workflow is with Inspector.

After you sign up at the link above, make sure to set the INSPECTOR_INGESTION_KEY variable in the application environment file to monitoring Workflow execution:

.env

INSPECTOR_INGESTION_KEY=nwse877auxxxxxxxxxxxxxxxxxxxxxxxxxxxx